Conventionally, vehicles equipped with a rotating electric machine as a driving source, such as hybrid vehicles, electric automobiles, and fuel cell electric vehicles are known. Such a vehicle is equipped with a battery or the like for storing electric power to be supplied to an electric motor. The battery stores electric power generated at the time of regenerative braking or electric power generated by a generator equipped on the vehicle.
Incidentally, also known is a vehicle that is charged by supplying electric power to a battery equipped on the vehicle from a electric power source external to the vehicle such as a electric power source in a house. By connecting a socket provided in a house and an inlet provided in the vehicle with a cable, electric power is supplied to the battery of the vehicle from the electric power source in the house. Hereinafter, a vehicle that charges a battery equipped on the vehicle by a electric power source disposed external to the vehicle is also referred to as a plug-in vehicle.
In a plug-in vehicle, for further reducing the cost required for charging of the battery, it is supposed to charge the battery in the middle of night when the electric power rate is generally set low. However, in the hybrid vehicle, the battery is managed so that a certain state of charge (SOC) that allows traveling by the rotating electric machine is constantly ensured. Therefore, the charging amount of the battery in the middle of night is limited.
For addressing this, there is proposed a technique of varying a target range or a target value of the state of charge of the battery so as to charge the battery with much more electric power in the middle of night.
Japanese Patent Laying-Open No. 2007-62638 (Patent Document 1) discloses a hybrid car including a chargeable/dischargeable electric power storage device for supplying electric power to a rotating electric machine, a electric power input unit for receiving the electric power supplied from a source external to the vehicle to charge the electric power storage device, a generator for generating electric power using output from an internal combustion engine and supplying the generated electric power to the electric power storage device, a controller for controlling a charging state of the electric power storage device to a predetermined control range or control target value, and an input device for switching the predetermined control range or control target value.
In the hybrid car described in this publication, the electric power storage device can be charged by receiving the electric power externally given to the electric power input unit of the vehicle. Also, when the SOC of the electric power storage device decreases during traveling, the electric power storage device can be charged by driving the internal combustion engine and the generator. On the other hand, the SOC of the electric power storage device is controlled to a predetermined control range or control target value. Specifically, when the SOC of the electric power storage device decreases, the controller drives the internal combustion engine and the generator to change the electric power storage device. Here, in this hybrid car, since the predetermined control range or control target value can be switched by the input device, when the vehicle is to arrive at a location where charging is possible (for example, home where charging equipment is installed) in a time zone where electric power rate is low (for example, midnight electric power time zone), the predetermined control range or control target value can be set lower than usual by the input device. As a result, the electric power charged in the electric power storage device is actively used during the traveling until the vehicle arrives at the chargeable location, and a charging amount from the external electric power source at the chargeable location can be increased, with the result that more low-price electric power can be applied for charging.